Britain's Labour Party, which suffered a crushing defeat in last week's election, must rebuild its economic credibility and become more supportive of the business world to return to power, said Andy Burnham, the frontrunner in Labour's leadership race.

Britain's largest trade union has threatened to sever links with the opposition Labour Party and deprive it of millions of pounds in funding if the party's next leader tries to move it too far to the centre ground of British politics.